Разница между параллельным тестированием и тестированием поперечного браузера

Cross Browser Testing: When we do crossbrowser testing we
execute multiple test scripts on different browsers one by
one. When one test executed/completed another browser
would be invoked on the current browser.

--Parallel Execution: In parallel testing multiple browsers are
invoked simultaneously and all the test scripts are executed
parallelly.
Obedient Ocelot